Areas of endemism

Quantitative evaluations of species distributional congruence allow evaluating previously proposed biogeographic regionalization and even identify undetected areas of endemism. The geographic scenery of Northwestern Argentina offers ideal conditions for the study of distributional patterns of species since the boundaries of a diverse group of biomes converge in a relatively small region, which also includes a diverse fauna of mammals. In this paper we applied a grid-based explicit method in order to recognize Patterns of Distributional Congruence (PDCs) and Areas of Endemism (AEs), and the species (native but non-endemic and endemic, respectively) that determine them. Also, we relate these distributional patterns to traditional biogeographic divisions of the study region and with a very recent phytogeographic study and we reconsider what previously rejected as 'spurious' areas. Finally, we assessed the generality of the patterns found. The analysis resulted in 165 consensus areas, characterized by seven species of marsupials, 28 species of bats, and 63 species of rodents, which represents a large percentage of the total species (10, 41, and 73, respectively). Twenty-five percent of the species that characterize consensus areas are endemic to the study region and define six AEs in strict sense while 12 PDCs are mainly defined by widely distributed species. While detailed quantitative analyses of plant species distribution data made by other authors does not result in units that correspond to Cabrera's phytogeographic divisions at this spatial scale, analyses of animal species distribution data does. We were able to identify previously unknown meaningful faunal patterns and more accurately define those already identified. We identify PDCs and AEs that conform Eastern Andean Slopes Patterns, Western High Andes Patterns, and Merged Eastern and Western Andean Slopes Patterns, some of which are re-interpreted at the light of known patterns of the endemic vascular flora. Endemism do not declines towards the south, but do declines towards the west of the study region. Peaks of endemism are found in the eastern Andean slopes in Jujuy and Tucumán/ Catamarca, and in the western Andean biomes in Tucumán/Catamarca. The principal habitat types for endemic small mammal species are the eastern humid Andean slopes. Notwithstanding, arid/semi-arid biomes and humid landscapes are represented by the same number of AEs. Rodent species define 15 of the 18 General Patterns, and only in one they have no participation at all. Clearly, at this spatial scale, non-flying mammals, particularly rodents, are biogeographically more valuable species than flying mammals (bat species). RESUMEN. Patrones de endemicidad de pequeños mamíferos en el Noroeste de Argentina. Las evaluaciones cuantitativas de congruencia distribucional de las especies permiten comparar regionalizaciones biogeográficas propuestas previamente e incluso identificar áreas de endemismo que no han sido detectadas. El escenario geográfico del Noroeste Argentino ofrece condiciones ideales para el estudio de patrones de distribución de especies. En este artículo aplicamos un método explícito basado en cuadrículas con el objetivo de reconocer Patrones de Congruencia Distribucional (PDCs) y Áreas de Endemismo (AEs), así como las especies (nativas pero no endémicas y endémicas, respectivamente) que las determinan, para examinar las relaciones de las especies de micromamíferos con las principales unidades ambientales. Adicionalmente, relacionamos estos patrones distribucionales con las divisiones biogeográficas tradicionales de la región estudiada y con un estudio fitogeográfico muy reciente y reconsideramos lo que previamente rechazamos como 'áreas espurias'. Finalmente, evaluamos la generalidad de los patrones encontrados. El análisis resultó en 165 áreas consenso, caracterizadas por siete especies de marsupiales, 28 especies de murciélagos y 63 especies de roedores, lo que representa un gran porcentaje del total de especies (10, 41 y 73, respectivamente). Veinticinco por ciento de las especies que caracterizan las áreas consenso son endémicas a la región estudiada y definen seis AEs en sentido estricto, mientras que 12 PDCs están principalmente definidos por especies ampliamente distribuidas. Mientras que los análisis cuantitativos de la distribución de especies de plantas no resultan en unidades que coincidan con las divisiones fitogeográficas de Cabrera a esta escala espacial, los análisis de la distribución de especies animales muestran patrones que sí se corresponden con tales divisiones. Identificamos patrones de distribución de la fauna significativos y definimos más adecuadamente aquellos ya identificados. Identificamos PDCs y AEs que conforman los Patrones de las Pendientes Andinas del Este, los Patrones Andinos Altos del Oeste y los Patrones de las Pendientes Andinas Este y Oeste Fusionados, algunos de los cuales son re-interpretados a la luz de patrones conocidos de la flora vascular endémica. El endemismo no declina hacia el sur, pero sí hacia el oeste de la región estudiada. Los picos de endemismo se encuentran en las pendientes del este de los Andes en Jujuy y Tucumán/Catamarca, y en los biomas andinos del oeste en Tucumán/Catamarca. El tipo de hábitat principal para las especies endémicas de mamíferos pequeños está en las pendientes húmedas del este de los Andes. A pesar de esto, los biomas áridos y semiáridos y los paisajes húmedos están representados por el mismo número de AEs. Las especies de Rodentia definen 15 de los 18 Patrones Generales (GPs), y sólo en uno de ellas no participaron. Claramente, a esta escala espacial, los mamíferos no voladores, particularmente los roedores, son biogeográficamente más valiosos que los mamíferos voladores.

Quantitative evaluations of species distributional congruence allow evaluating previously proposed biogeographic regionalization and even identify undetected areas of endemism. The geographic scenery of Northwestern Argentina offers ideal conditions for the study of distributional patterns of species since the boundaries of a diverse group of biomes converge in a relatively small region, which also includes a diverse fauna of mammals. In this paper we applied a grid-based explicit method in order to recognize Patterns of Distributional Congruence (PDCs) and Areas of Endemism (AEs), and the species (native but non-endemic and endemic, respectively) that determine them. Also, we relate these distributional patterns to traditional biogeographic divisions of the study region and with a very recent phytogeographic study and we reconsider what previously rejected as 'spurious' areas. Finally, we assessed the generality of the patterns found. The analysis resulted in 165 consensus ...

Track analysis is the core of panbiogeographic analysis. In this work, we reflect on the formalization of track analysis, its methodological issues, and interpretations by using new software developments and from a
contemporary evolutionary biogeographical viewpoint. From a geometric perspective, we analyze the meaning of a minimal spanning tree, considering that Prim’s algorithm is the most commonly used to draw individual tracks. We then show the existing methodologies (graphs, PAE, combined method, AE) and software packages (Trazos2004, Croizat, Martitracks, fossil) used to perform track analysis. Finally, we illustrate a track analysis using Nearctic mammals as an example. Based on our review, connectivity matrix analysis may be the best way to associate individual tracks into generalized tracks because it compares the minimal spanning tree topologies. However, it is the most demanding of all methods, since it requires a high spatial congruence among species, and therefore more algorithmic development.